Slash command autocomplete prioritizes recency over prefix matching

Current behavior:
Typing /q autocompletes to /frontend-design (or other recently-used commands) even though "q" doesn't match any characters in that command name.

Expected behavior:
Prefix matching should take priority over recency. If I type /q, show commands starting with "q" first. Only fall back to fuzzy/recency matching when there are no prefix matches.

Why this matters:

• Muscle memory fails when recency hijacks results
• Users expect /q to show /quit or similar, not unrelated recent commands
• The current behavior makes autocomplete unpredictable

Suggested fix:

1. Exact prefix matches first
2. Fuzzy prefix matches second (e.g., /fd → /frontend-design)
3. Recency-weighted results last (only when no character matches exist)